A tyre (also spelled as tire) is a ring-shaped covering which fits around a rim of a wheel of a vehicle. The tyre protects the wheel and enables better vehicle performance. Also, tyres provide traction between the vehicle and the road surface along with providing a flexible cushion which absorbs shock. Modern pneumatic tyres are made up of synthetic rubber, natural rubber, fabric and wire, along with carbon black and other chemical compounds. Usually, the tyres consist of a thread and a body. The thread is the part of the tyre which comes in contact with the road surface. Also, the thread provides grip with the road surface. Generally, the tyre with a thick rubber or rubber/composite compound formulated provides an appropriate level of traction and does not wear away too quickly. However, the tyres gradually wear down over the course of continuous usage. Also, the tyres wear down due to aggressive driving, or steering and alignment problems. Usually, the threads of tyres are gradually worn out since the threads are in contact with road surface. The wearing of threads of the tyres result in baldness of tyre and hence the tyre is termed as bald tyre.
Bald tyres are dangerous because limited thread reduces traction for the vehicle, which can be very dangerous in wet or icy driving conditions. Further, bald tyres results in tyre blowouts. Baldness of tyres results in fatal consequences leading to injury and casualty for both the driver or rider and living beings in the vicinity of the vehicle since baldness results in slithering of the vehicle. Ideally, tyres are required to be replaced before the tyre is truly bald. The driver is required to check the tyres often to ensure that the tyre thread depth is safe. Usually, tyres are usable until the tyre thread depth reaches 1/16 of an inch (0.15 centimeters). Such depth of the tyre is termed as the “re-threading level of the tyre”.
In conventional systems, penny test is a common method to assess tyre safety i.e. to check the depth of the threads. Penny test is a manual method, where a coin is inserted between the threads of the tyre. If the coin doesn't go enough inside the threads, then the tyre has to be replaced. However, penny test is not a reliable method for testing the tyre life since each time the driver needs to place the coin to check the thread depth which is a manual method. Conventionally, a number of wear indicators are embedded at a predetermined location of the threads. Upon wearing of the tyre, the wear indicators become visible. The indicators provide an indication for tyre replacement upon wearing of the tyre.
U.S. Pat. No. 5,303,756 discloses a visually distinctive material embedded in the tyre that gets exposed when threads wear down. Further, U.S. Pat. No. 4,226,274 provides for a wear indicator which is in the form of a letter ‘K’. The indicator is embedded in the thread provides a quantitative measure of the amount of thread remaining from being worn out. Additionally, the wear indicator provides visual signals when the tyre is worn out. However, the conventional methods do not provide indication to the driver on wearing of the tyre before wearing of the tyre takes place.
In one conventional method, the wear of tyre is detected based on number of rotations of the tyre. Particularly, upon reaching a desired number of rotations of the tyre, the wear of tyre is indicated. However, such a way of indication involves huge processing power and time where the number of rotations needs to be calculated at regular intervals of time.
In one conventional method, tyres i.e. sidewalls are illuminated using optical fibres to indicate visibility of the moving vehicle on roads. However, such a way of illumination does not imply the wear of tyre.
Hence, there is a need for a method for detecting and indicating the baldness of the tyre when rethreading level is reached.